1. Field:
This invention is in the field of telemetry alarm systems in which a sensor is located at a site remote from the alarm center and in which the signal from the sensor is supplied to the alarm center via telemetry transmissions. In particular, the alarm system of the invention is adapted for use by the mining and related industries to continuously monitor slope stability, especially in open-cut operations such as in the surface mining of copper, so that instances of slope instability will be indicated at an alarm center.
2. State of the Art:
Many different types of telemetry alarm systems are presently known, but none are adapted to monitor slope stability. Some of the known systems are provided with means to discriminate between valid and invalid information at the receiver by imposing a minimum time limitation that must be met before a received transmission is deemed valid. In some, one or more tone signals are superimposed upon the transmitted signal to indicate a valid signal.